Optical waveguide chips, which contain one or more planar waveguides, are used as optical components in constructing an optical communication system. In order for an optical waveguide chip to function as an optical component in an optical communication system, optical fibers are connected to the planar optical waveguides formed in the optical waveguide chip. In providing this connection, the optical waveguide chip is first positioned and fixed in a special casing, and an optical fiber is then abutted against one end of the planar optical waveguide. The optical fiber to be connected to the waveguide is first properly positioned to allow maximum light transition, and then bonded thereto by an adhesive or other suitable means.
U.S. Pat. No. 5,297,228 teaches a method for connecting an optical fiber to a planar optical waveguide by which an end face of a waveguide chip, in which planar optical waveguides are formed, is abutted against an end face of a fiber aligning jig, on which optical fibers are arranged, to thereby connect the optical fiber to the corresponding planar optical waveguide. In the method disclosed in the '228 patent, at least one marker is formed in each of the waveguide chips and the fiber aligning jigs, and also at least one pin guide groove is formed in each of the waveguides and the fiber aligning jigs, using the marker as a reference mark. The reference markers are necessary because the Si substrate, from which the waveguide chip and the fiber aligning jigs are made, has metallic luster. V-grooves are cut on the surfaces of the waveguide chip and the fiber aligning jigs by slicing to prevent unwanted movement after axis aligning procedures.
U.S. Pat. No. 5,280,550 discloses a method for coupling an optical fiber to an optoelectronic component having an optical waveguide embedded in a substrate, the waveguide opens into a notch formed on a first face of the substrate. The method disclosed in the '550 patent includes the steps of: (1) pre-positioning the optical fiber in a V-shaped groove of an optical fiber support, the groove terminating at a first surface of the optical fiber support; (2) positioning the fiber support such that the first surface of the substrate and the first surface of the fiber support are directly opposite each other, the first faces forming a gap therebetween; and (3) positioning an end of the optical fiber to be in the notch such that the waveguide and the optical fiber are optically aligned. The V-shaped grooves of the fiber support are obtained by molding method.
U.S. Pat. No. 4,966,433 discloses a optical device in which a substrate-supported waveguide is aligned with an optical fiber. The optical alignment is facilitated by locating the optical fiber in a preferentially etched groove in the substrate supporting the waveguide. Optical coupling is facilitated by a ledge structure overhanging a sloping etched wall of a groove holding the fiber.
U.S. Pat. No. 5,175,781 discloses a method of attaching an optical fiber to an integrated optic chip which includes the step of first forming an alignment groove in the waveguide surface of the integrated optic chip by utilizing a laser ablation system to remove a predetermined portion of the integrated optic chip material. Then, a transversal groove is cut normal to the alignment groove. An optical fiber is disposed within the alignment groove, and the fiber core is optically aligned with the optical axis of the waveguide by translational and rotational positioning of the fiber end face adjacent to the cut surface.
U.S. Pat. No. 5,217,568 discloses a process for etching a silicon substrate to form a V-groove by first applying a coating of a poly(benzocyclobutene) resin on the substrate. Selected portions of the polymer coating layer was removed to expose the underlying silicon, whereby the remaining coating protects the silicon at the adjacent region. Finally, the substrate is contacted with an alkaline solution to anisotropically etch the exposed silicon at the selected region to form a groove.
U.S. Pat. No. 5,046,809 discloses a coupling arrangement for optically coupling a fiber to a planar optical waveguide integrated on a substrate in silicon micro mechanical units. The coupling arrangement provides a fiber arranged in a V-shaped groove of the substrate, leading to the planar waveguide and terminating in a low-attenuation butt coupling between the fiber and the planar optical waveguide. The V-shaped grooves are manufactured by anisotropic etching in a silicon crystal having the orientation 100.
U.S. Pat. Nos. 5,197,109, 5,018,817, 4,953,936, 4,810,049, 4,522,463, and 4,217,032 also disclose optical coupling devices involving optical fibers and waveguides. In all the optical coupling arrangements disclosed hereinabove, the fiber-guiding grooves, which can be formed by etching, mechanical cutting, or laser cutting, are a very important element which provide the desired alignment. However, at the present time, it is still difficult to precisely, and with good repeatability, control the depth of the optical fiber-guiding grooves. The difficulty is more profound with the reactive ion etching technique to form these grooves, which typically have a depth of greater than 35 .mu.m and preferably should have an error within 0.5 .mu.m. At the present time, the error is typically greater than about 2 .mu.m when the grooves are formed using the reactive ion etching technique. This error greatly and adversely affects the repeatibility in the light coupling efficiency between optical fibers and the waveguide.